Self-locking self-pierce riveting: a new self-pierce riveting technology for multi-material applications in lightweight car body structures

Abstract

Due to the fact that car attributes like the dynamic drive ability, CO2 emissions and efficiency are factors which are massively influenced by the total vehicle mass; lightweight becomes a key issue in modern car body design. Nowadays, most cost-effective lightweight solutions can be achieved by multi-material design. This restricts conventional thermal joining technologies and shows the demand for cost-effective and efficient mechanical and adhesive joining technologies. This paper shows the development of a new type of a self-pierce riveting system with solid rivets for joining lightweight materials such as ultra-high-strength steels or aluminium in multi-material structures. Compared to the conventional solid self-pierce riveting, the embossing ring is not located at the die but just below the protruding head of the joining element. While processing, the die-sided material is deformed by the stamp-sided material, which is deformed by the embossing ring. A modified die with an enlarged surface area is used to significantly reduce the deformations of the die-sided material. Besides experimental studies, the process simulation (FEM) is used to achieve an optimum geometry of the rivet. This paper presents detailed information about the development of the new riveting technology and the characteristics of the new joining technology compared to the conventional solid self-pierce riveting. Joints with the new solid self-locking self-piercing rivet show slight deformations of die-sided sheets, high process stability and flexibility.